In conducting an investigation of a crime, forensic personnel use various visual markers to measure and document identifying characteristics of physical evidence. Such markers are typically positioned next to an item of evidence and then photographed to provide a documentary record of the evidence (memorializing). These photographed markers can then be used in trial to show visual indicia on them that permit characterization of the item of evidence, such as height and width.
Photographic documentation of crime and accident scenes, medical conditions and the like typically include one or more straightedged forensic scale(s) within the photographic view in order to establish scale and orientation so that accurate measurements of size, shape, and relative position may be later determined by analysis of the photograph. Coroners and other forensic personnel such as medical and dental doctors and the like typically want to document irregularly shaped individual, and/or a pattern of multiple, wounds or stains on a body surface, and presently use one or more straightedge or right angle scales laid on the body around the area of interest. The specialized field of forensic scales is dominated by a few suppliers who provide a limited line of products that vary mainly in color (e.g., black, white) and types of scale markings (e.g., front face only, both front and back, metric, English, etc.). The overall scale dimensions are effectively standardized to a few common lengths, widths and thicknesses.
A typical example of how forensic scales are used by forensic personnel (“users”) is as follows:                1. An area of crime evidence, such as a wound, blood stain, birthmark, etc. (typically on a body) is being documented.        2. A forensic scale, preferably a right angle scale, is placed so that the wound (for example) is near the inside corner of the scale.        3. A photo is taken of the wound with the scale also in view. This allows detailed measurements to be accurately made on the photograph, even if magnified for closer examination.        4. The photograph may be taken under ultraviolet lighting because body fluids like blood and semen fluoresce, making them more visible.        5. If there are several wounds in a large pattern, a larger scale may be needed.        
Unfortunately, the evidence area is often too large for the range of scale sizes that the user has available. In that case, two or more scales are typically placed around the area. For the best accuracy in measurement, the scales should be placed either end to end to form a continuously linear straightedge with scale markings spaced correctly across the junction; or at right angles, where the scale markings share a common zero point at the inside vertex, and the straight edges are exactly ninety degrees apart.
Obviously, it is difficult to achieve perfect alignment, spacing, and angles, especially if laid out on the irregular contours of a person's body. The work-around in use now is to utilize a computer to manipulate the photographic image as needed to create an accurate grid of measurement intervals, but then that may cause questions about validity of the evidence.
U.S. Pat. No. 6,880,277 (Kaminski; 2005) discloses a plural-part evidence marker comprising at least two flat marker elements (20) bearing visual indicia thereon, and a substantially rigid leg unit (30) connecting and detachably securing the at least two flat marker elements at an angle (preferably ninety degrees) with respect to one another. The leg unit consists of six identical, orthogonally disposed legs (32) substantially shorter than the pair of edges (22) of the flat marker elements. Each of the six legs of the leg unit preferably has four orthogonal grooves (34) formed longitudinally therein. Each groove is capable of receiving an edge of one of the flat marker elements therein, retaining one of the flat marker elements therein by friction.
It can be seen that Kaminski's evidence marker does not provide a common scale marking zero point to align two or more scales to accurately measure evidence, therefore this requires forensic personnel to calculate the distance between two scales connected according to Kaminski's disclosure. Furthermore, the separation distance and relative angle between Kaminski's connected scales can change because the leg unit frictionally holds the scales on only one edge, which allows the scales to be inadvertently moved out of relative position while in use. There is also a vertical leg that interferes with use in a planar configuration.
U.S. Pat. No. 2,394,983 (Clarkson; 1944) discloses a scale assembly comprising an adapter (11) for assembling and holding a pair of companion scales or ruler-equipped scales at right angles to each other. A regular triangular ruler (5) equipped with a suitably graduated scale (6); and a conventional flat-type double beveled ruler or scale (8) equipped with a scale (10) are used, wherein one end of the flat ruler (8) is mitered (9) and thus suitably beveled to conformably associate its graduated scale (10) with the graduated scale (6) of the triangular ruler (5).
It can be seen that Clarkson's scale assembly, while using existing scales, requires modification (mitering) of at least one scale/ruler in order to enable right angle positioning plus alignment of scale markings of two scales when they are assembled using Clarkson's adapter. Clarkson's scale assembly also relies on a flat surface to hold the assembled scales at a fixed right angle.
The prior art discloses other ways to connect scales at fixed relative angles while also aligning their scale markings, but in general they require specially formed or modified scales. In other words, the prior art typically works with custom scales, not pre-existing ones. Examples of this prior art include U.S. Pat. Nos. 5,208,992, 5,353,509, 5,392,525, 5,440,818, 6,033,282, 6,141,882, 6,247,240, 6,851,196, and 7,082,692.
Thus there is an unmet need in the market for a means of combining existing, unmodified scales to create arbitrary larger, optionally multi-armed scales for use by crime investigators, particularly forensic personnel, in varied measuring situations. Therefore, it is an object of the present invention to provide a scale coupling system that works with existing, unmodified scales to form a coupled scale with at least two forensic scales being coupled at a scale joint wherein the coupling means maintains measurement accuracy of scale markings across the scale joint, and assures angular accuracy of a fixed angle scale joint including linearity along one hundred eighty degree joined scale arms.